My greener friends are increasingly troubled by the lack of a rise in recent global surface temperatures. Using monthly data measured as the departure from long-term averages, there’s been no significant warming trend since the fall of 1996. In other words, we are now in our 17th year of flat temperatures.
Since 1900, the world has seen one other period of similar temperature stagnation (actually a slight cooling) that lasted for 30 years and ended around 1976. The current one is happening with much more putative warming “pressure,” because the atmosphere’s carbon-dioxide content is much higher than it was in mid-century.
From the Industrial Revolution to 1950, atmospheric carbon-dioxide concentrations rose by about 15 percent. Today, the increase is up to 41 percent, making long periods without warming either 1) increasingly unlikely, or 2) the natural result of simply overestimating how “sensitive” surface temperature is to carbon dioxide. My money is on the latter.
Now, just for fun, let’s assume that on Jan. 1, another warming trend began, at the same rate that was observed in the last such period, from 1977 through 1998, or 0.17 C per decade.
Running a large experimental sample reveals that, on average, the rate of warming will have to continue through 2020 before a statistically significant trend emerges in the post-1996 data. (Remember that a “trend” that does not meet the normal grounds for significance is one that cannot scientifically be distinguished from “no trend.”)
In other words, it’s a pretty good bet that we are going to go nearly a quarter of a century without warming.
In response, the climate establishment is becoming increasingly polarized, with a growing number of researchers calculating less warming this century, while the apocalyptics, such as NASA’s James Hansen, simply edge out further on increasingly thin limbs.
This is quite a change. In 2002, I published a paper, “Revised 21st Century Temperature Projections,” which used a variety of independent sources and generally predicted a range of 21st century warming of 1.0 to 3.0 C. In response, the 2009 “Climategate” emails revealed a number of surreptitious attempts and schemes to either get the paper removed, get the esteemed geographer who was the relevant editor of the journal Climate Research fired from his University of Auckland professorship, or, if all else failed, destroy the journal itself.